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pamstretch - scale up a PNM or PAM image by interpolating between pixels.
pamstretch [-xscale=X] [-yscale=Y]
[-blackedge] [-dropedge] N [infile]
You can use the minimum unique abbreviation
of the options. You can use two hyphens instead of one. You can separate
an option name from its value with white space instead of an equals sign.
pamstretch scales up pictures by integer values, either vertically,
horizontally, or both. pamstretch differs from pnmscale and pnmenlarge
in that when it inserts the additional rows and columns, instead of making
the new row or column a copy of its neighbor, pamstretch makes the new
row or column an interpolation between its neighbors. In some images, this
produces better looking output.
To scale up to non-integer pixel sizes, e.g.
2.5, try pamstretch-gen(1)
instead.
Options let you select alternative methods
of dealing with the right/bottom edges of the picture. Since the interpolation
is done between the top-left corners of the scaled-up pixels, it's not obvious
what to do with the right/bottom edges. The default behaviour is to scale
those up without interpolation (more precisely, the right edge is only
interpolated vertically, and the bottom edge is only interpolated horizontally),
but there are two other possibilities, selected by the blackedge and
dropedge options.
The N parameter is the scale factor. It
is valid only if you don't specify -xscale or -yscale. In that case, pamstretch
scales in both dimensions and by the scale factor N.
- -xscale=X
- This
is the horizontal scale factor. If you don't specify this, but do specify
a vertical scale factor, the horizontal scale factor is 1.
- -yscale=Y
- This
is the vertical scale factor. If you don't specify this, but do specify
a horizontal scale factor, the vertical scale factor is 1.
- -blackedge
- interpolate to black at right/bottom edges.
- -dropedge
- drop one (source) pixel
at right/bottom edges. This is arguably more logical than the default behaviour,
but it means producing output which is a slightly odd size.
Usually
produces fairly ugly output for PBMs. For most PBM input you'll probably
want to reduce the `noise' first using something like pnmnlfilt(1)
.
pamstretch-gen(1)
,
pnmenlarge(1)
, pnmscale(1)
, pnmnlfilt(1)
Russell Marks (russell.marks@ntlworld.com).
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